Comparison of the optical (top) and near-infrared (bottom) spectra at bolometric maximum for the He-star explosion models he4–he12. There is a clear separation between models that show He I lines (at 5876, 6678, 7065, 10 830, 20 581 Å) and those that do not. Model he9 is an intermediate case. The presence or absence of He I lines is easy to see in the optical. He I 10830 Å overlaps with O and Mg lines so a feature is seen in this spectral region irrespective of the He content. He I 20 581 Å gives a clear signature. We also note that all models have about the same color at maximum (modulo the strength of lines). For He I line identifications, see Fig. 4.